A. Field of the Invention
The present invention relates to a capacitor assembly that includes a plurality of capacitors connected to a common connection interface, and in particular, to a capacitor assembly that can include a plurality of capacitors efficiently contained inside a single, easily mounted and removed housing.
B. Problems in the Art
The need has been identified for a set of capacitors that can be assembled as an integrated unit. Preferably the unit would be easily installable or removable from an electrical cabinet.
One example of use would be for relatively high power lighting systems where a main capacitor, of relatively high capacitance value, assists in control of operating power to a lamp (e.g., a relatively high wattage, high intensity discharge (HID) lamp, such as 1,000 watts or more). One such system is disclosed in U.S. Pat. No. 4,994,718 and available commercially under the trademark MULTI-WATTT™ from Musco Corporation of Oskaloosa, Iowa, USA.
A system which uses one or more smaller capacitors selectively hooked in parallel with a main capacitor to selectively add incremental amounts of capacitance to the lamp circuit to increase operating power to the lamp is commercially available under the SMART LAMP™ system available from Musco Corporation of Oskaloosa, Iowa, USA. See also published U.S. Patent Application No. 2005/0184681 A1, which is incorporated by reference in its entirety herein. Each lamp circuit would have such a capacitor combination available to it.
Normally single, can-type capacitors, as well as other parts of the lamp circuits (and other electric components) are individually mounted in an electrical cabinet. Space is a consideration for these individual capacitors. It is desirable they be as space-efficient as possible. It is desirable for multiple capacitors to be enclosed in a single mountable housing in an efficient manner.
As mentioned, it is desirable and advantageous to be able to quickly and easily, without special tools, install and remove capacitors from an electrical box. U.S. Pat. No. 6,969,304, (incorporated by reference herein in its entirety) to Musco Corporation discloses one example of a quick connect bracket for relatively large can-type capacitors. A bolt or rod on a bracket holding the capacitor basically can be laid or placed into a U-shaped receiver that is screwed, bolted or welded to a vertical wall of the electrical box. The capacitor can thus be relatively quickly and easily mounted or removed.
There are additional needs that have been identified for a multiple capacitor assembly for these types of applications. One is heat management. Because the capacitors are handling high levels of electrical current, effective electrical and heat insulation is important. Volumetric efficiency is also important. By this it is referred to whether the package for the capacitors effectively utilizes the space in which the entire capacitor occupies to perform not only its capacitance function but its electrical and heat insulation functions.
Efficient electrical connection of the multiple capacitors to the lamp circuit is also important. There cannot be substantial electrical losses or costly or fragile connections. Also, access to the capacitors is important.
Finally, especially for sports or other wide area lighting applications like the examples given herein, robustness and long-term durability, as well as economy and efficiency of operation, are important. Sports lighting systems are designed and desired to last for decades. They are frequently in outdoor environments and are therefore exposed to a wide variety of temperatures and conditions. Also, as previously mentioned, capacitors for lamp circuits are normally installed in electrical boxes. Other components are required. Therefore, efficient size and use of space is important.
Heretofore, the state of the art primarily used relatively large can-type main capacitors for each lamp. There was not much concern about enclosing them in a housing or packaging plural capacitors as an integrated unit for collective quick mount and dismount. However, the SMART LAMP™ system does use plural capacitors per lamp because of its innovation of changing operating power to a lamp by incrementally increasing capacitance in the lamp circuit during operating life.
Some state of the art capacitors utilize a conventional plastic dielectric insulating material inside their capacitor cans or cases. If there is a failure of this type of capacitor, it can result in overheating. If the level of overheating gets high enough, it can cause melting or combustion of the plastic material. It has been found that this combustion or overheating releases gases and smoke that can deposit or literally cover the entire interior of an electrical box. Moreover, they can damage or detrimentally affect other electrical components and essentially ruin the entire electrical box and its contents. And, of course, if combustion occurs, the danger and risk of fire and ancillary problems, such as electrical shock, can occur.
Therefore, a need has been identified for an improved multi-capacitor assembly of the type that is useful at least for applications of the nature described above.